DETERMINATION OF THE STABILITY OF DILUTED ALLERGEN EXTRACTS USING A CONCENTRATION STEP PRIOR TO EAST INHIBITION

Background Generally the stability of diluted allergen extracts, as us ed for skin testing, provocation testing and immunotherapy can not be measured using a normal enzyme allergosorbent test (EAST) inhibition m ethod. Objective The aim of this study was to determine the stability of diluted allergen extracts using an ultrafiltration step prior to th e standard EAST inhibition procedure, in which the allergen extract wa s concentrated 100-fold. Methods This concentration procedure was vali dated for Dermatophagoides pteronyssinus, timothy pollen, birch pollen and cat dander extracts and used in a stability study in which three batches were stored for 1 year at 6 degrees C and 25 degrees C. Result s There was no difference in relative potency before and after concent ration of birch and timothy pollen extracts. D. pteronyssinus and cat dander extracts showed a significant decrease of 25% and 35% of the re lative potency after concentration. The mean coefficient of variation of 12 determinations of the stability study was 11.8%. Conclusion For all allergens the 30 BU/mL or approximately 0.00025 mg/mL solution was stable for 12 months at both temperatures, except for D. pteronyssinu s which declined rapidly at 25 degrees C.